Behavior of Individual Pulverized Asphaltenes in a Tube Furnace under Inert Atmosphere

Abstract

Oil sands found in Athabasca and Cold Lake regions of Northern Alberta form Canada’s primary source of energy reserves. Asphaltenes, a significant part of bitumen is often considered to be the least valuable component of crude oil due to various factors such as difficulty in transporting and processing. However, utilization of asphaltenes plays a crucial role in overall economics of oil sands extraction. Gasification of asphaltenes can result in much needed hydrogen for upgrading of bitumen. Pyrolysis is the first step in gasification that directs formation of soot on one hand and char formation on the other. However, very limited study has been carried out on pyrolysis of asphaltenes in entrained bed conditions. Single particle investigations are useful since they are conducted in a well-controlled environment allowing elimination of complexities arising from particle-particle interactions. In this work, pyrolysis of pulverized Asphaltenes feedstock was carried out in a drop tube furnace (DTF) maintained in atmospheric pressure. Effect of furnace temperature and particle size on char formation and char characteristics were investigated. Chars obtained from higher particle size (1.7mm to 0.85mm) at 600˚C, 700˚C and 800˚C exhibited similar morphology to that of pure asphaltenes while pyrolysis of particle sizes ranging from 250-425µm at higher temperatures (700-900˚C) demonstrated better results with 10-2% volatile matter remaining in char. SEM as well as cross sectional images of char particles indicated formation of cenospheres and fragmentation of char particles at higher pyrolysis temperatures. High pyrolysis temperatures also implicated loss of active sites, increase in alkene content and aromatic condensation. ICP MS investigation validated retention of K and Na along with heavy elements such as V, Ni and Cu at temperatures above 700ᵒC. Morphology of char obtained at different oxygen partial pressures was also examined. Ultimately, the combustion reactivities of char obtained at 700ᵒC, 800ᵒC and 900ᵒC for particle sizes 425µm-0.85mm, 355-425µm and 250-355µm were compared.